Foundry MCP Server

A simple, lightweight and fast MCP (Model Context Protocol) server that provides Solidity development capabilities using the Foundry toolchain (Forge, Cast, and Anvil).

Overview

This server connects LLM assistants to the Foundry ecosystem, enabling them to:

• Interact with nodes (local Anvil instances or remote RPC endpoints)
• Analyze smart contracts and blockchain data
• Perform common EVM operations using Cast
• Manage, deploy, and execute Solidity code and scripts
• Work with a persistent Forge workspace

Features

Network Interaction

• Start and manage local Anvil instances
• Connect to any remote network (just specify the RPC)
• Get network/chain information

Contract Interaction

• Call contract functions (read-only)
• Send transactions to contracts (if PRIVATE_KEY is configured)
• Get transaction receipts
• Read contract storage
• Analyze transaction traces
• Retrieve contract ABIs and sources from block explorers

Solidity Development

• Maintain a dedicated Forge workspace
• Create and edit Solidity files
• Install dependencies
• Run Forge scripts
• Deploy contracts

Utility Functions

• Calculate contract addresses
• Check contract bytecode size
• Estimate gas costs
• Convert between units (hex to decimals, etc.,)
• Generate wallets
• Get event logs
• Lookup function and event signatures

Smart Contract Analysis (Heimdall)

• Disassemble EVM bytecode into human-readable opcodes
• Decode raw calldata without requiring ABI
• Decompile EVM bytecode to Solidity source code and ABI
• Generate visual control flow graphs for EVM bytecode
• Detailed transaction inspection with calldata decoding and trace analysis

Usage

The server is designed to be used as an MCP tool provider for MCP Clients. When connected to a client, it enables the clients(claude desktop, cursor, client, etc.,) to perform Solidity and onchain operations directly.

Requirements

• Node.js v18+
• Foundry toolchain (Forge, Cast, Anvil)
• Heimdall-rs (for smart contract analysis)

Manual Setup

1. Ensure Foundry tools (Forge, Cast, Anvil) are installed on your system:

   curl -L https://foundry.paradigm.xyz | bash
   foundryup
   

2. Clone and build the server.

   bun i && bun build ./src/index.ts --outdir ./dist --target node
   
   

3. Update your client config (eg: Claude desktop):

 "mcpServers": {
    "foundry": {
      "command": "node",
      "args": [
        "path/to/foundry-mcp-server/dist/index.js"
      ],
      "env" :{
        "PRIVATE_KEY": "0x1234",
      }
    }
 }

[!NOTE] PRIVATE_KEY is optional

Setup using NPM Package

You can now install and run the server directly using npm:

Global Installation

npm install -g @pranesh.asp/foundry-mcp-server

Direct Usage with npx

npx @pranesh.asp/foundry-mcp-server

MCP Client Configuration

Claude Code

 claude mcp add-json foundry-mcp-server '{"type":"stdio","command":"npx","args":["@pranesh.asp/foundry-mcp-server"],"env":{"RPC_URL":"","PRIVATE_KEY":""}}'   

Other MCP Clients (Cursor, Claude, Windsurf)

Add to your MCP settings:

{
  "mcpServers": {
    "foundry": {
      "command": "npx",
      "args": ["@pranesh.asp/foundry-mcp-server"],
      "env": {
        "RPC_URL": "http://localhost:8545",
        "PRIVATE_KEY": "0x..."
      }
    }
  }
}

Configuration

The server supports the following environment variables:

• RPC_URL: Default RPC URL to use when none is specified (optional)
• PRIVATE_KEY: Private key to use for transactions (optional)

[!CAUTION] Do not add keys with mainnet funds. Even though the code uses it safely, LLMs can hallicunate and send malicious transactions. Use it only for testing/development purposes. DO NOT trust the LLM!!

[!TIP] Getting Invalid configuration errors? Check your JSON syntax—common issues include double quotes (""KEY" → "KEY"), trailing commas, or unquoted keys. Validate with echo '...' | jq .

Workspace

The server maintains a persistent Forge workspace at ~/.mcp-foundry-workspace for all Solidity files, scripts, and dependencies.

Tools

Anvil

• anvil_start: Start a new Anvil instance
• anvil_stop: Stop a running Anvil instance
• anvil_status: Check if Anvil is running and get its status

Cast

• cast_call: Call a contract function (read-only)
• cast_send: Send a transaction to a contract function
• cast_balance: Check the ETH balance of an address
• cast_receipt: Get the transaction receipt
• cast_storage: Read contract storage at a specific slot
• cast_run: Run a published transaction in a local environment
• cast_logs: Get logs by signature or topic
• cast_sig: Get the selector for a function or event signature
• cast_4byte: Lookup function or event signature from the 4byte directory
• cast_chain: Get information about the current chain

Forge

• forge_script: Run a Forge script from the workspace
• install_dependency: Install a dependency for the Forge workspace

File Management

• create_solidity_file: Create or update a Solidity file in the workspace
• read_file: Read the content of a file from the workspace
• list_files: List files in the workspace

Utilities

• convert_eth_units: Convert between EVM units (wei, gwei, hex)
• compute_address: Compute the address of a contract that would be deployed
• contract_size: Get the bytecode size of a deployed contract
• estimate_gas: Estimate the gas cost of a transaction

Heimdall Analysis

• heimdall_disassemble: Disassemble EVM bytecode into human-readable opcodes
• heimdall_decode: Decode raw calldata without requiring ABI
• heimdall_decompile: Decompile EVM bytecode to Solidity source code and ABI
• heimdall_cfg: Generate visual control flow graph for EVM bytecode
• heimdall_inspect: Detailed inspection of Ethereum transactions

Usage in Claude Desktop App 🎯

Once the installation is complete, and the Claude desktop app is configured, you must completely close and re-open the Claude desktop app to see the tavily-mcp server. You should see a hammer icon in the bottom left of the app, indicating available MCP tools, you can click on the hammer icon to see more details on the available tools.

Now claude will have complete access to the foundry-mcp server. If you insert the below examples into the Claude desktop app, you should see the foundry-mcp server tools in action.

Examples

1. Transaction analysis:

Can you analyze the transaction and explain what it does? 
https://etherscan.io/tx/0xcb73ad3116f19358e2e649d4dc801b7ae0590a47b8bb2e57a8e98b6daa5fb14b

1. Querying Balances:

Query the mainnet ETH and USDT balances for the wallet 0x195F46025a6926968a1b3275822096eB12D97E70.

1. Sending transactions:

Transfer 0.5 USDC to 0x195F46025a6926968a1b3275822096eB12D97E70 on Mainnet. 

1. Deploying contracts/Running scripts:

Deploy a mock ERC20 contract to a local anvil instance and name it "Fire Coin".

Acknowledgments ✨

• Model Context Protocol for the MCP specification
• Anthropic for Claude Desktop

Disclaimer

The software is being provided as is. No guarantee, representation or warranty is being made, express or implied, as to the safety or correctness of the software. They have not been audited and as such there can be no assurance they will work as intended, and users may experience delays, failures, errors, omissions, loss of transmitted information or loss of funds. The creators are not liable for any of the foregoing. Users should proceed with caution and use at their own risk.